The cabin to be used by passengers of an aircraft defines a pressurised space that can also contain the pilot's cabin or the cockpit.
The level of loads induced by pressurisation is taken into account in the design of an aircraft and has a special influence on the design of the structure delimiting the cabin that must withstand these loads.
The capability of a structure to resist such loads depends particularly on the geometry of this structure.
The approximately cylindrical geometry of the structure delimiting the passenger cabin in conventional aircraft is particularly favourable for resistance to pressurisation loads.
However, a structure of this type has to be closed by sealed bottoms that are inherently more sensitive to pressurisation loads, at its two longitudinal ends. Consequently the means for fastening these bottoms onto the structure have to be conservatively designed.
Furthermore, an approximately cylindrical geometry limits possibilities for increasing the passenger carrying capacity of aircraft.
Conversely, a wide cabin geometry provides a greater carrying capacity, but does not have such a good natural capability of resisting pressurisation loads. Under pressurisation loads, such a structure tends to move back into an almost circular shape. The term “wide” geometry refers to a structure in which the dimension along the transverse direction of the aircraft is larger than its extent along the vertical direction of the aircraft. The less good capability of the structure to resist pressurisation loads then makes necessary to increase the mass of the structure and/or use stronger but usually more expensive materials.